Acoustic device



Feb. 25, 1930. BOXLEY 1,748,632

ACOUSTI C DEVICE Filed Sept. 9, 1926 IN V EN TOR.

A TTORNEYSj Patented Feb. 25, 1930' PATENT OFFICE FREDERICK BOXLEY, OF OAKLAND, CALIFORNIA ACOUSTIC DEVICE Application filed September 9, 1926. Serial No. 134,358.

. This invention relates to acoustic devices for sound reproducers and especially to diaphragms capable of reproducing and amplifying sound vibrations of a phonograph rec- '5 rd or the high frequency vibration of a telephone receiver, a radio loud speaker unit or the like.

The .object of the present invention is to generally improve and simplify the construction'and operation of sound reproducing dial phragms; to provide a sound reproducing j diaphragm of the cone-shaped type in which the diaphragm .may be materially decreased and the total area presented materially ining which leaves the peripheral edge of the diaphragm entirely free and unsupported so that the Vibrations transmitted to the diaphragm will bodily move the same throughout its entire area.

One form which the invention may assume is shown by way of illustration in the accompanying drawings, in which:

' Figure l is a central vertical longitudinal section of a loud speaker cabinet showing'a loud speaker unit mounted therein and also the diaphragm forming the subject matter of the present application,

Figure 2 shows a modified form of diaphragm.

Referring to thedrawings in detail and particularly to Figure 1, A indicates a sounding board of suitable construction, B a loud speaker unit and C thediaphragm. The diaphragm together with the vibrating unit a'ctuating the same is, in this instance, enclosed within acabinet in which 4 indicates the base, 3 the front grill through which the sound waves are emitted and 2 the top, the soundinafter be described.

Any suitable vibratory type of unit may be creased and further to provide a novel mounte 'ing board being suitably secured between the employed but in the present instance, a balanced armature type is illustrated, in which 5 indicates the armature, 6 the pivot about which it vibrates and 7 a link connection between the armature and the vibrating arm 8. The function of vibratory units of this character is well understood and a detailed description of the circuits actuating the same is thought unnecessary. Sufiiceth to say that when the unit is connected with a radio set, current pulsations of high frequency are set up in the unit. and the armature is thereby swung about its pivot 6, the movement of the armature being transmitted through the'connection 7 to the vibrating arm 8 and rod 9 which is, accordingly, reciprocated or'vibrated on the line ofits longitudinal axis and as the diaphragm C is directly attached thereto, the entire diaphragm will be bodily moved throughout its entire area.

- The diaphragm, in turn, reacts with the sounding board A and the audible sound waves are projected through the grill 3 in the usual manner. The construction of the diaphragm and mounting thereof is exceeding- 1y important. It consists of two sections generally indicated at 11 and 12, the member 11 being cone-shaped and the member 12 a frusto-conical shell. The cone is inverted with relation to the frusto-conical shell that is the apex of the cone is pointed in the direction of the largest diameter of the shell. The periphery of the cone is flanged as indicated at 14 and is glued or otherwise secured to the small end of the shell. One end of the shell is, in this manner closed and a diaphragm of large area and small diameter is obtained which reacts with the sounding board A to produce the audible sound waves. In actual practise, I have found that the diaphragm as a whole should be left free and unobstructed as far as possible, as the clearest reproduction or sound transformation is thereby obtained. In this instance, the rod 9 extends through the apex of the cone 11 and is rigidly secured thereto in any suitable manner,.for instance, by furls 15 and the screws '16. This mannerof securing theidiaphragm with relation to the vibrati rod 9 leaves the peripheral edge of the coiie and the shell 12 entirely free and unsup orted and the entire diaphragm is, accor ingly,

moved throughout its entire area when the vibrations are transmitted through the rod. To further insure free transmission of the vibrations a flexible support for the outer end of'the rod 9 is desired. In the resent instance, a-bracket 17 is employed an a rubber bearing or sleeve 18 is placed in the upper end thereof. The outer end of the 'rod 9 rests in the rubber bearing and resistance to vibratory movement is thereby reduced to a minimum.

The cone 11 and shell 12 may be'constructed of paper, celluloid, metal and other suitable materials and in actual practise parch ment, pa r or the like has been successfullyemploye The exact thickness of the aper is not Important as itis found that the (l zee er tones are best reproduced when the diaphragm is fairly heavy and that the high- Eitched tones are best reproduced with a lower tones. The

ghter cone, and for this reason two cones are I)illustrated', the one at C and the second at 7 Where two are employed one diaphragm will be constructed of a heavier material and the other of a lighter material and substantial erfect reproduction is obtained, as one diaphragm will take care of higher pitched tones and the second willtake care ofv the diaphragms may be ointed in the same direction or they may e-reversed with relation to each other, as

desired. For instance, the rod 9 might be extended through the arm 8 and the speaker unit and the sounding board A. The second diaphra could thus .be laced on the opposite si e of the sounding oard.

Numerous modifications of this character can of course, be resorted to and any detailed description thereof is'thought unnecessary. In Figure 2 a modified form of the diaphragm is illustrated. In that instance corrugations are formedin the cone 11, as indicated at 19. When the cone is constructed in this manner, part of the vibrations are absorbed in, the cone and the remaining vibrations are transmitted to the shell. Ex-. cellent tone reproductions are obtained in either case.

While certain features of the present invention are more or less specifically described, I wish it understood that various changes may be resorted to within the scope of the appended claims. Similarly thatvarious materials and finishes of the several parts employed may be such asthe manufacturer may decide or varying conditions or uses may demand. 'Having thus described my invention, what 'Iclaim and desire. to secure by Letters Patent is -1. An ac'oustic device comprising a rod connectedat one end with a v1 ratory sound reproducer, a cup-shaped- -with the open endof t 1,74a,esa

reproducer, a support for the opposite end of the rod and a diaphragm secured to the rod at a point intermediate the ends thereof, said diaphragm having its peripheral edge entirely free and unsupported so that vibrations transmitted to the rod will bodily move the diaphragm throughout its entire .area.

.2. An acoustic device com rising a rod connected at one end with a v1 ratory sound reproducer, a flexible support for the opposite end of the rod and a diaphragm secured to the rod at its central point and intermediate the ends of the rod, said dia hragm having its peripheral edge entirely ee and unsupported so that vibrations transmitted to the rod will bodily move the diaphragm throughout its entire area.

3 n acoustic device of the character de scr bed, a diaphragm comprising a frustpconical shaped shell open at one end, and a cone-shaped diaphragm forming a closure for the smaller open end of the shell.

.4. In an acoustic device of the character described, a diaphragm comprisin a frustocon cal shaped s ell, and a conical ia hragm secured in. the small end thereof, t eapex of the cone pointing in the direction of the larger end of the shell. i

5. In an acoustic device of the character described, a diaphra comprisin a frustoconical shaped shel a conical i-aphragm secured in the small end thereof, the apex of the cone pointin in the direction of the lar eroend of the s ell, a rod in the longitu al axisof the shell, and the cone and connected at one end with a vibrating sound reproducer, and means whereby the rod is secured to the apex of the cone.

6. An acoustic device.c0m rising a rod connected at one end with a vi rating sound reproducer, and a cup-shaped "diaph secured to the rod and bodily movable with the rod.

7. An acoustic device comprising a-rod connected at one end-with a vibrating sound diaphragm. secured to the rod and bodily movable with the rod, and a soundin e'diaphragm:

a rod 8. An acoustic device com rising connected at one end with a v1 rato'ry sound reproducer and a cup-sha ed diaphragm secured tothe rod and b0 ily movable with the rod, the side of the c'up-sha ed diaphragm flaring from top to bottom lifiea cone with the largest diameter at the top or open end.

9. An acoustic device of the character deboard (mo-operating scribed comprising a frusto-conical shaped shell open at one end, a cone-sha d diaphragm forming a closure for the smallzr end of the shell, and'corr tions formed in a portion of the surfaceo the cone-shaped diaphragm.

FREDERICK BOXLEY. 

